Should an audio system be left on at all times?

Knownothing - I think so. Capacitor companies like Nichicon mention only temperature as limiting factor (and not the rush current).

My experience and reading make me believe that the powering up and down produce more wear. I have transistor amps 25 years old I leave on all the time. I have never heard of heat being a factor in amp deterioration . I have often heard of an amp going bad from not being used. I think this is another case where theory and the real world differ. The ONLY argument I have ever heard against leaving them on is the cost of the power. In every case where I have seen this discussed the author has stated that leaving them on prolongs their life.

Interesting. I listen to music pretty much every evening I am home. That would mean turning the system on and off everyday. I agree with other posts that it takes time for the wires to warm up (I have long runs of speaker cable), so what is the difference in waiting for the amp and other electronics to come to operating temperature too? I have been leaving my gear on thinking it was better for longevity. Maybe its time to rethink that.

Stanwal - I stated what capacitor companies claim. Going bad when not used, that you mentioned, has place when you not use amp for long time (years) and aluminum oxide layer (serving as isolator) depletes eventually lowering allowable voltage and causing short at operating voltage - often exploding from the heat build-up. Caps have fuse (rubber plug) to prevent explosion. It is recommended in such cases to start at lower voltage (Variable transformer) until aluminum oxide layer will build-up again. Unfortunately some power supplies like SMPS either start or not and varying line voltage might not help much.

It is very difficult to compare performance of 25 year old amp with exactly same new one. I replaced power supply cap in old SS amp and got bass control and dynamics I didn't know it had.

I think that capacitors are just drying up and the temperature accelerates it. It might not fail ever but performance will slowly deteriorate since caps ESR rises up (thats why people recap their amps).

Stanwall - Check this link: http://www.dfrsolutions.com/pdfs/Uprating_of_Electrolytic_Capacitors.pdf

They mention temperature as main factor (and 10 deg C rule). ESR while getting lower at high temperatures (might explain reason for warmup) eventually gets higher from electrolyte evaporation.

Good quality amp equipped with 105 deg C caps might last for very long time while luke warm. I would like to preserve my amp at current state as long as I can.